I live in the city, and outside of the college campuses and MUPs (where you see more cruiser bars), the ratio of drop bars to flat bars is so high that I notice* when someone has flat bars. I see flat bars mostly used by men on the inner city park trails. I don't hang out by off-road trails though, so my sample group is skewed.

This isn't very statistically accurate (TOM!), but when I'm just out and about in the city, the majority of handlebars used by people over 21 are cruiser bars of some type on cruiser bikes. Next comes drop bars...almost every commuter I see has drop bars, but I live over 10 miles from either downtown, so they're putting on some miles daily. I see flat bars maybe 15% of the time, way more if on a MUP (maybe 50/50 there). I also see a lot more drop bars at the private colleges than at the U of M.